/**
 * Copyright 2017 Kailash Dabhi (Kingbull Technology)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package omrecorder;

import android.media.AudioFormat;

/**
 * A  Header to be appended to the end of Wav audio file
 *
 * @author Kailash Dabhi
 * @date 26-07-2016
 */
final class WavHeader {
  private final PullableSource pullableSource;
  private final long totalAudioLength;

  WavHeader(PullableSource pullableSource, long totalAudioLength) {
    this.pullableSource = pullableSource;
    this.totalAudioLength = totalAudioLength;
  }

  /** Returns the {@code WavHeader} in bytes. */
  public byte[] toBytes() {
    long sampleRateInHz = pullableSource.config().frequency();
    int channels =
        (pullableSource.config().channelPositionMask() == AudioFormat.CHANNEL_IN_MONO ? 1 : 2);
    byte bitsPerSample = pullableSource.config().bitsPerSample();
    return wavFileHeader(totalAudioLength - 44, totalAudioLength - 44 + 36, sampleRateInHz,
        channels, bitsPerSample * sampleRateInHz * channels / 8, bitsPerSample);
  }

  private byte[] wavFileHeader(long totalAudioLen, long totalDataLen, long longSampleRate,
      int channels, long byteRate, byte bitsPerSample) {
    byte[] header = new byte[44];
    header[0] = 'R'; // RIFF/WAVE header
    header[1] = 'I';
    header[2] = 'F';
    header[3] = 'F';
    header[4] = (byte) (totalDataLen & 0xff);
    header[5] = (byte) ((totalDataLen >> 8) & 0xff);
    header[6] = (byte) ((totalDataLen >> 16) & 0xff);
    header[7] = (byte) ((totalDataLen >> 24) & 0xff);
    header[8] = 'W';
    header[9] = 'A';
    header[10] = 'V';
    header[11] = 'E';
    header[12] = 'f'; // 'fmt ' chunk
    header[13] = 'm';
    header[14] = 't';
    header[15] = ' ';
    header[16] = 16; // 4 bytes: size of 'fmt ' chunk
    header[17] = 0;
    header[18] = 0;
    header[19] = 0;
    header[20] = 1; // format = 1
    header[21] = 0;
    header[22] = (byte) channels;
    header[23] = 0;
    header[24] = (byte) (longSampleRate & 0xff);
    header[25] = (byte) ((longSampleRate >> 8) & 0xff);
    header[26] = (byte) ((longSampleRate >> 16) & 0xff);
    header[27] = (byte) ((longSampleRate >> 24) & 0xff);
    header[28] = (byte) (byteRate & 0xff);
    header[29] = (byte) ((byteRate >> 8) & 0xff);
    header[30] = (byte) ((byteRate >> 16) & 0xff);
    header[31] = (byte) ((byteRate >> 24) & 0xff);
    header[32] = (byte) (channels * (bitsPerSample / 8)); //
    // block align
    header[33] = 0;
    header[34] = bitsPerSample; // bits per sample
    header[35] = 0;
    header[36] = 'd';
    header[37] = 'a';
    header[38] = 't';
    header[39] = 'a';
    header[40] = (byte) (totalAudioLen & 0xff);
    header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
    header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
    header[43] = (byte) ((totalAudioLen >> 24) & 0xff);
    return header;
  }
}